Engine device

ABSTRACT

An exhaust gas purification device (27) including: a first case (28) communicating with an exhaust manifold (6) of an engine (1) and internally including a first exhaust gas purification body (30) for removing a carbon compound; and a second case (29) communicating with an exhaust outlet of the first case (28) and internally including second exhaust gas purification bodies (31 to 33) for removing a nitrogen compound. The first case (28) and the second case (29) are arranged above the engine (1) and in an L-shape to respectively extend along two side surfaces of the engine (1), the two side surfaces being adjacent to each other.

TECHNICAL FIELD

The present invention relates to an engine device, such as a dieselengine, to be mounted in, e.g., an agricultural machine (a tractor, acombine harvester) or a construction machine (a bulldozer, a hydraulicexcavator, a loader), and specifically to an engine device equipped withan exhaust gas purification device for removing, e.g., a particulatematter (soot, particulates) contained in the exhaust gas or a nitrogenoxide (NOx) contained in the exhaust gas.

BACKGROUND ART

Traditionally, there have been known techniques for purifying an exhaustgas from a diesel engine by introducing the exhaust gas into an exhaustgas purification device (an exhaust gas aftertreatment device) disposedin an exhaust gas path of the diesel engine, the exhaust gaspurification device being constituted by a case internally including adiesel particulate filter (hereinafter, such a case will be referred toas a DPF case) and a case internally including a urea selectivereduction catalyst (hereinafter, such a case will be referred to as aselective catalytic reduction (SCR) case) (see, e.g., Patent Literatures1 and 2 (hereinafter, referred to as PTLs 1 and 2)).

CITATION LIST Patent Literature

-   PTL 1: Japanese Patent No. 5543563-   PTL 2: Japanese Patent No. 5244334

SUMMARY OF INVENTION Technical Problem

In a configuration as those in PTL 1 in which an exhaust gaspurification device constituted by a DPF case and an SCR case disposedin parallel is attached to an engine, an area required for mounting theexhaust gas purification device on the engine device is large. Thisleads to upsizing of the engine device, which is disadvantageous. Inaddition, in a configuration in which the above-described exhaust gaspurification device is mounted above the engine device, a height of theengine device increases by a height of the exhaust gas purificationdevice.

PTL 2 discloses a configuration including a DPF case, a connecting pipehaving an inserted portion which is inserted into the DPF case and onwhich a plurality of through-holes is provided, and a urea waterinjection nozzle disposed at an end of the connecting pipe, wherein ureawater and an exhaust gas are mixed together. In this configuration, theconnecting pipe needs to have an adequate length. Otherwise, the ureaand the exhaust gas are not mixed adequately, which leads to a reductionin purification effect and to upsizing of the exhaust gas purificationdevice, disadvantageously.

Some aspects of the present invention have an object to provide anengine device that has been improved as a result of study of thecircumstances described above.

Solution to Problem

In order to attain the above object, an engine device according to anaspect of the present invention is an engine device including an exhaustgas purification device including a first case communicating with anexhaust manifold of an engine and internally including a first exhaustgas purification body for removing a carbon compound and a second casecommunicating with an exhaust outlet of the first case and internallyincluding a second exhaust gas purification body for removing a nitrogencompound, wherein the first and second cases are arranged above theengine in an L-shape to respectively extend along two side surfaces ofthe engine, the two side surfaces being adjacent to each other.

The engine device described above may be configured such that aturbocharger is interposed between the first case and the exhaustmanifold, and the first case and the turbocharger are connected to eachother in series above the exhaust manifold disposed close to, among thetwo side surfaces of the engine, a first side surface.

The engine device described above may be configured such that a flywheelhousing is disposed close to, among the two side surfaces of the engine,a second side surface intersecting the first side surface, and thesecond case is disposed above the flywheel housing.

The engine device described above may be configured such that the secondcase is disposed below the first case, and the first case and the secondcase are connected to each other via a urea mixing tube in a position inwhich the first case and the second case overlap each other in a planview.

The engine device described above may be configured such that aurea-water injection body for injecting urea water into the first caseis fixed to a portion of an outer peripheral surface of the first case,the portion being in the position in which the first case and the secondcase overlap each other in a plan view, the portion being not a portionof the first case through which the urea mixing tube is inserted intothe first case.

The engine device described above may be configured such that a part ofthe second exhaust gas purification body is a selective catalyticreduction filter made of a particulate-matter collection filter to whicha catalytic component for urea selective catalytic reduction is applied.

The engine device described above may be configured such that aurea-water injection body for injecting urea water into a urea mixingtube is disposed in a portion of the first case that is close to theexhaust outlet of the first case, and the urea mixing tube has both endsrespectively inserted into the exhaust outlet of the first case and anexhaust inlet of the second case to allow the first case and the secondcase to communicate with each other.

The engine device described above may be configured such that the ureamixing tube has a first inserted portion that is inserted into the firstcase, the first inserted portion extending toward the urea-waterinjection body, the first inserted portion having a tube wall on whichan exhaust introduction opening is bored, the exhaust introductionopening allowing an exhaust gas having passed through the first exhaustgas purification body to be introduced into the urea mixing tube.

The engine device described above may be configured such that the ureamixing tube has a second inserted portion that is inserted into thesecond case, the second inserted portion having a distal end that istapered, the second inserted portion extending to a position apart froman inner wall surface of the second case.

The engine device described above may be configured such that a mixerfor stirring and mixing urea water with an exhaust gas is internallyincluded in a second inserted portion of the urea mixing tube, thesecond inserted portion being inserted into the second case.

The engine device described above may be configured such that a mixerfor stirring and mixing urea water with an exhaust gas is disposed inthe first inserted portion of the urea mixing tube, the first insertedportion being inserted into the first case.

The engine device described above may be configured such that the secondcase is disposed below the first case, and the first case and the secondcase are connected to each other via the urea mixing tube in a positionin which the first case and the second case overlap each other in a planview.

Advantageous Effects of Invention

According to the aspect of the present invention, the first and secondcases are arranged in an L-shape above the engine. Thus, the first andsecond cases can be arranged dispersedly in a space above the engine.Consequently, the top surface side of the engine device can be made low.Thus, upsizing of the engine device including the exhaust gaspurification device can be suppressed or reduced, and the engine devicehaving a compact size can be mounted in a limited space of an engineroom of, e.g., a work machine.

According to the aspect of the present invention, the turbocharger andthe first case can be compactly disposed above the exhaust manifold.Consequently, the top surface side of the engine device can be made low.In addition, a passage from an outlet of the exhaust manifold to thefirst case can be made shorter. Furthermore, the turbocharger and thefirst case can be rigidly supported at a side surface of the engine viathe exhaust manifold.

According to the aspect of the present invention, the second case isdisposed above the flywheel housing. Consequently, the second case canalso be disposed compactly in the space above the flywheel housing.Thus, upsizing of the engine device including the exhaust gaspurification device can be suppressed or reduced.

According to the aspect of the present invention, the second case isdisposed below the first case, and the first case and the second caseare connected to each other via the urea mixing tube in the position inwhich the first case and the second case overlap each other in a planview. Consequently, the connected portion between the first case and thesecond case can be made shorter. This makes it possible to suppress orreduce the phenomenon that an exhaust gas passing through the ureamixing tube is influenced by a temperature of outside air, therebymaking it possible to reduce the phenomenon that a crystal lump of aurea component is formed in the exhaust gas purification device.Consequently, it is possible to easily prevent an increase in exhaustresistance in the exhaust gas purification device that may otherwise becaused by, e.g., growth of the urea crystal lump.

According to the aspect of the present invention, the urea-waterinjection body is mounted in the first case, so that the urea-waterinjection body and the first case can be constituted as a single unit.This makes it easier to perform an assembling work for mounting theexhaust gas purification device onto the engine device.

According to the aspect of the present invention, the second case isprovided with the SCR filter. Thus, the collecting filter can be omittedfrom the first case. Accordingly, the first case can be downsized.Consequently, the engine device including the exhaust gas purificationdevice can be made compact.

According to the aspect of the present invention, the urea-waterinjection body is mounted in the first case, so that the urea-waterinjection body and the first case can be constituted as a single unit.This makes it easier to perform an assembling work for mounting theexhaust gas purification device onto the engine device. In addition,according to the aspect of the present invention, both the ends of theurea mixing tube are respectively inserted into the first and secondcases. Consequently, the inside of the urea mixing tube can bemaintained at a high temperature by a temperature atmosphere of theexhaust gas. This makes it possible to suppress or reducecrystallization of a urea component in urea water having been injectedinto the urea mixing tube.

According to the aspect of the present invention, the exhaustintroduction opening is provided on the tube wall of the urea mixingtube. Consequently, a flow velocity of an exhaust gas flowing throughthe urea mixing tube can be made uniform, and thus urea water sprayedfrom the urea-water injection body toward the inside of the urea mixingtube is more likely to be stirred and dispersed. This improves theevaporativity of the urea component at a low temperature, and alsoenhances the reaction efficiency between the exhaust gas and the ureacomponent.

According to the aspect of the present invention, the outlet-side end ofthe urea mixing tube has a squeezed shape. Consequently, urea water iscaused to collide with an inner wall surface of the outlet-side end ofthe urea mixing tube. This allows evaporation of an unreacted ureacomponent, thereby making it possible to facilitate a reaction betweenthe exhaust gas and the urea component in the second case. In addition,due to the configuration in which the outlet-side end of the urea mixingtube is apart from the second case, it is possible to prevent the ureacomponent from reaching an inner wall surface of the second case,thereby making it possible to suppress or reduce the phenomenon that acrystal lump is formed on the inner wall surface of the second case.

According to the aspect of the present invention, the mixer internallyincluded in the urea mixing tube is positioned in the first case or thesecond case. This makes it possible to suppress or reduce a temperaturedrop in the mixer. In addition, since the exhaust gas whose flowvelocity has been made uniform in the urea mixing tube flows into themixer, a rotation performance of the mixer is made uniform. Thisfacilitates mixing of the urea water with the exhaust gas, therebymaking it possible to enhance the evaporativity of the urea component.Thus, it is possible to prevent crystallization of the urea component atthe mixer. Not only this, it is also possible to facilitate a reactionbetween the exhaust gas and the urea component, and to suppress orreduce the phenomenon that the urea water in the form of droplets entersthe second case.

According to the aspect of the present invention, the second case isdisposed below the first case, and the first case and the second caseare connected to each other via the urea mixing tube in the position inwhich the first case and the second case overlap each other in a planview. Consequently, the connected portion between the first case and thesecond case can be made shorter. This makes it possible to suppress orreduce the phenomenon that an exhaust gas passing through the ureamixing tube is influenced by a temperature of outside air, therebymaking it possible to reduce the phenomenon that a crystal lump of aurea component is formed in the exhaust gas purification device.Consequently, it is possible to easily prevent an increase in exhaustresistance in the exhaust gas purification, device that may otherwise becaused by, e.g., growth of the urea crystal lump.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A right side view of a diesel engine according to a firstembodiment.

FIG. 2 A left side view of the diesel engine according to the firstembodiment.

FIG. 3 A plan view of the diesel engine according to the firstembodiment.

FIG. 4 A back view of the diesel engine according to the firstembodiment.

FIG. 5 An explanatory diagram showing a cross-section of an exhaust gaspurification device according to the first embodiment, taken in a rightside.

FIG. 6 An explanatory diagram showing a cross-section of the exhaust gaspurification device according to the first embodiment, taken in a backside.

FIG. 7 An explanatory diagram showing a cross-section of an exhaust gaspurification device including a urea mixing tube according to a firstmodification, taken in a right side.

FIG. 8 An explanatory diagram showing a cross-section of the exhaust gaspurification device including the urea mixing tube according to thefirst modification, taken in a back side.

FIG. 9 An explanatory diagram showing a cross-section of an exhaust gaspurification device including a urea mixing tube according to a secondmodification, taken in a right side.

FIG. 10 An explanatory diagram showing a cross-section of the exhaustgas purification device including the urea mixing tube according to thesecond modification, taken in a back side.

FIG. 11 A right side view of a diesel engine according to a secondembodiment.

FIG. 12 A plan view of the diesel engine according to the secondembodiment.

FIG. 13 A back view of the diesel engine according to the secondembodiment.

FIG. 14 An explanatory diagram showing a cross-section of an exhaust gaspurification device according to the second embodiment, taken in a backside.

FIG. 15 A side view of a work vehicle in which the diesel engine ismounted.

FIG. 16 A plan view of the work vehicle.

FIG. 17 A back view of a diesel engine according to a third embodiment.

FIG. 18 A left side view of a tractor in which the diesel engine ismounted.

FIG. 19 A plan view of the tractor.

DESCRIPTION OF EMBODIMENTS First Embodiment

With reference to the drawings (FIGS. 1 to 6), the following willdescribe a first embodiment in which the present invention isimplemented. FIG. 1 is a right side view of a diesel engine 1, showing aright side on which an exhaust manifold 6 is disposed. FIG. 2 is a leftside view of the diesel engine 1, showing a left side on which an intakemanifold 3 is disposed. FIG. 3 is a plan view of the diesel engine 1,showing a side on which a cylinder head cover 12 is disposed. FIG. 4 isa back view of the diesel engine 1, showing a side on which a flywheelhousing 8 is disposed. The side of the diesel engine 1 on which theexhaust manifold 6 is disposed is referred to as a right side of thediesel engine 1. The side of the diesel engine 1 on which the intakemanifold 3 is disposed is referred to as a left side of the dieselengine 1. The side of the diesel engine 1 on which a cooling fan 24 isdisposed is referred to as a front side of the diesel engine 1.

Next, with reference to FIGS. 1 to 4, a configuration of the whole ofthe diesel engine 1 will be described. The diesel engine 1 includes acylinder head 2 having one side surface on which the intake manifold 3is disposed. The cylinder head 2 is mounted above a cylinder block 5including an engine output shaft 4 (crankshaft) and pistons (notillustrated). The cylinder head 2 has another side surface on which theexhaust manifold 6 is disposed. Front and rear ends of the engine outputshaft 4 respectively protrude from front and back side surfaces of thecylinder block 5.

The cylinder block 5 has a back surface to which the flywheel housing 8is fixedly attached. In the flywheel housing 8, a flywheel 9 isdisposed. The flywheel 9 is pivotally supported at a rear end of theengine output shaft 4. A driving force of the diesel engine 1 is takenvia the flywheel 9. The cylinder block 5 has a lower surface on which anoil pan 11 is disposed. The cylinder head cover 12 is disposed adjacentto an upper surface of the cylinder head 2.

The intake manifold 3 is provided with an exhaust gas recirculation(EGR) device 15 for taking in an exhaust gas that is to be recirculated.An air cleaner (not illustrated) is connected to the intake manifold 3via a compressor case 25 of a turbocharger 17. External air having beensubjected to dust removal and purification by the air cleaner is sent tothe intake manifold 3 through the compressor case 25, and is thensupplied to cylinders of the diesel engine 1. With the configurationdescribed above, part of an exhaust gas emitted from the diesel engine 1to the exhaust manifold 6 is recirculated into the cylinders of thediesel engine 1 from the intake manifold 3 through the exhaust gasrecirculation device 15. Consequently, a combustion temperature of thediesel engine 1 drops. Accordingly, an amount of nitrogen oxide (NOx)emitted from the diesel engine 1 is reduced, and fuel efficiency of thediesel engine 1 is enhanced.

Above the exhaust manifold 6, the turbocharger 17 is disposed. Theturbocharger 17 includes the compressor case 25 including a built-inblower wheel and a turbine case 26 including a built-in turbine wheel.The exhaust manifold 6 has an outlet connected to an exhaust intake sideof the turbine case 26. The turbine case 26 has an exhaust emission sideconnected to an exhaust intake side of the exhaust gas purificationdevice 27. Namely, an exhaust gas emitted from the cylinders of thediesel engine 1 to the exhaust manifold 6 is discharged to the outsidethrough components such as the turbocharger 17 and the exhaust gaspurification device 27.

A coolant pump 21 by which coolant is caused to recirculate in thecylinder block 5 and a radiator 19 (see FIG. 16) is provided. Thecoolant pump 21 is disposed close to the side of the diesel engine 1 onwhich the cooling fan 24 is disposed. The coolant pump 21 and thecooling fan 24 are connected to the engine output shaft 4 via, e.g., aV-belt 22. With this configuration, the coolant pump 21 and the coolingfan 24 are driven. The coolant is sent from the coolant pump 21 into thecylinder block 5 via an EGR cooler 18 of the exhaust gas recirculationdevice 15, and cooling air is supplied from the cooling fan 24.Consequently, the diesel engine 1 is cooled.

As the exhaust gas purification device 27 for purifying an exhaust gasemitted from the cylinders of the diesel engine 1, a first exhaust gaspurification case 28 (hereinafter, referred to as a first case 28) thatis a oxidation catalyst (DOC) for removing particulate matters in theexhaust gas from the diesel engine 1 and a second exhaust gaspurification case 29 (hereinafter, referred to as a second case 29) thatis a urea selective catalytic reduction filter (SCRF) system forremoving a nitrogen oxide in the exhaust gas from the diesel engine 1are provided.

The first case 28, which is a DOC case, internally includes an oxidationcatalyst 30 as an exhaust gas purification body. For example, theoxidation catalyst 30 is made of a wall-through type ceramic honeycombor a metal mesh on which a catalytic component (e.g., platinum (Pt)and/or palladium (Pd)) for facilitating an oxidation reaction of carbonmonoxide (CO) and/or hydrocarbon (HC) is carried. Thus, by causing anexhaust gas from the diesel engine 1 to pass through the first case 28,carbon monoxide (CO) and/or hydrocarbon (HC) in the exhaust gas isreduced.

The second case 29, which is an SCRF case, internally includes, as anexhaust gas purification body, an SCR filter 31 for urea selectivecatalytic reduction, an SCR catalyst 32 for urea selective catalyticreduction, and an ammonia slip catalyst (ASC) 33. The SCR filter 31 ismade of, e.g., a particulate-matter (PM) collection filter to which anSCR catalyst component is applied. For example, the SCR filter 31 ismade of a wall-flow type ceramic honeycomb on which a catalyticcomponent (SCR catalyst component) for facilitating NOx selectivecatalytic reduction is carried. For example, the SCR catalyst 32 is madeof a wall-through type ceramic honeycomb, a metal mesh, or the like onwhich a SCR catalyst component is carried. The ammonia slip catalyst 33is an oxidation catalyst for oxidizing ammonia not reacted in the SCRfilter 31 and the SCR catalyst 32. Thus, by causing an exhaust gas fromthe diesel engine 1 to pass through the second case 29, a nitrogen oxide(NOx) in the exhaust gas is reduced.

The first case 28 has an elongated cylindrical shape extending inparallel to the output shaft (crankshaft) 4 of the diesel engine 1 in aplan view. The second case 29 has an elongated cylindrical shapeextending in a direction orthogonal to the output shaft 4 of the dieselengine 1 in a plan view. Namely, the exhaust gas purification device 27includes the first case 28 and the second case 29 each of which has anelongated cylindrical shape and which are arranged in an L-shape in aplan view to extend along an outer periphery of the cylinder head 2 ofthe diesel engine 1.

The first case 28 has an exhaust gas inlet connected to an exhaust gasoutlet of the turbine case 26 in the turbocharger 17, and also has alongitudinal intermediate portion connected to the cylinder head 2 via acase support bracket 34. The first case 28 is disposed adjacent to oneside (right side) of the cylinder head 2, and is linearly aligned withthe turbocharger 17 at a height substantially identical to that of theturbocharger 17. Namely, the first case 28 and the turbocharger 17 areconnected in series above the exhaust manifold 6. Consequently, even ina case where the first case 28 of the exhaust gas purification device 27is mounted in the diesel engine 1, the height of the diesel engine 1 canbe made low. Thus, the diesel engine 1 can be mounted even in an engineroom having a limited space.

The second case 29 is fixed above the flywheel housing 8 via a casesupport bracket 35. The second case 29 is positioned at a lower positionthan the first case 28. The first case 28 and the second case 29 arearranged in an L-shape such that a part 28 a downstream in an exhaustgas traveling direction (hereinafter, such a part will be referred to asan exhaust-gas downstream part 28 a) of the first case 28 and a part 29a upstream in the exhaust gas traveling direction (hereinafter, such apart will be referred to as an exhaust-gas upstream part 29 a) of thesecond case 29 overlap each other in a top-and-bottom direction. Thefirst case 28 and the second case 29 are connected to each other via anexhaust communicating tube 36 at the exhaust-gas downstream part 28 aand the exhaust-gas upstream part 29 a, which overlap each other in thetop-and-bottom direction. A urea-water injection body 76 for injectingurea water into the first case 28 is fixed to a portion of an outerperipheral surface of the first case 28. This portion of an outerperipheral surface of the first case 28 is in the position in which thefirst case 28 and the second case 29 overlap each other in a plan view,and is not a portion of the first case 28 to which the exhaustcommunicating tube 36 is attached.

The first case 28 is rigidly supported, by the turbocharger 17 and thecase support bracket 34, at a side surface (right side surface) of thediesel engine 1, the side surface being close to the exhaust manifold 6.Meanwhile, the second case 29 is rigidly supported, by the first case 28and the case support bracket 35, at a side surface (back surface) of thediesel engine 1, the side surface being close to the flywheel housing 8.Consequently, the exhaust gas purification device 27 can be rigidlysupported in a space adjacent to an outer periphery of the cylinder head2 and above the exhaust manifold 6 and the flywheel housing 8. Inaddition, the diesel engine 1 provided with the exhaust gas purificationdevice 27 can be made compact.

The first case 28 has a shape reduced toward a downstream side in theexhaust gas traveling direction such that a cross-section of theexhaust-gas downstream part 28 a is smaller than that of a part 28 b inwhich the exhaust gas purification body is mounted (hereinafter, such apart will be referred to as an exhaust-gas-purification-body mountedpart 28 b). The first case 28 is configured such that the exhaust-gasdownstream part 28 a is disposed closer to the center of the first case28 than is the exhaust-gas-purification-body mounted part 28 b.Consequently, an outer peripheral surface of the exhaust-gas downstreampart 28 a is closer to the center of the first case 28 than is an outerperipheral surface of the exhaust-gas-purification-body mounted part 28b. This can create, in the vicinity of the outer peripheral surface ofthe exhaust-gas downstream part 28 a, a space in which the urea-waterinjection body 76 can be mounted.

The second case 29 has a shape reduced toward an upstream side in theexhaust gas traveling direction such that a cross-section of theexhaust-gas upstream part 29 a is smaller than that of a part 29 b inwhich the exhaust gas purification bodies 31 to 33 are mounted(hereinafter, such a part will be referred to as anexhaust-gas-purification-body mounted part 29 b). The second case 29 isconfigured such that lower ends of exhaust-gas upstream part 29 a andthe exhaust-gas-purification-body mounted part 29 b are positioned atsubstantially identical heights. This provides a sufficient spacebetween the exhaust-gas downstream part 28 a of the first case 28 andthe exhaust-gas upstream part 29 a of the second case 29, which aredisposed to overlap each other in different positions in thetop-and-bottom direction. Consequently, a urea mixing tube 39, which isinternally included in the exhaust communicating tube 36 connecting theexhaust-gas downstream part 28 a and the exhaust-gas upstream part 29 a,achieves a length allowing urea water and an exhaust gas to be mixedtogether adequately.

Injectors (not illustrated) in the respective cylinders of the dieselengine 1 are provided with a fuel pump 42 and a common rail 43 connectedto a fuel tank 45 illustrated in FIG. 15 (FIG. 16). The cylinder head 2has a side on which the intake manifold 3 is disposed, and the commonrail 43 and a fuel filter 44 are disposed adjacent to that side of thecylinder head 2. The fuel pump 42 is provided to the cylinder block 5,which is located below the intake manifold 3. Each of the injectors hasa fuel injection valve (not illustrated) of anelectromagnetically-controlled opening and closing type.

A fuel in a fuel tank 45 is sucked into the fuel pump 42 through thefuel filter 44. Meanwhile, a discharge side of the fuel pump 42 isconnected to the common rail 43, and the common rail 43, which has acylindrical shape, is connected to the injectors of the diesel engine 1.A surplus of the fuel forcibly fed from the fuel pump 42 to the commonrail 43 is returned to the fuel tank 45. Then, the high-pressure fuel istemporarily stored in the common rail 43, and the high-pressure fuel inthe common rail 43 is supplied into the cylinders of the diesel engine1.

With the configuration described above, the fuel in the fuel tank 45 isforcibly fed to the common rail 43 by the fuel pump 42, and thehigh-pressure fuel is stored in the common rail 43. In addition, thefuel injection valves of the injectors are controlled to be opened andclosed, so that the high-pressure fuel in the common rail 43 is injectedto the cylinders of the diesel engine 1. Namely, by electronicallycontrolling the fuel injection valves of the injectors, it is possibleto control a fuel injection pressure, a fuel injection timing, and afuel injection period (fuel injection amount) with high accuracy.Consequently, it is possible to reduce a nitrogen oxide (NOx) emittedfrom the diesel engine 1.

Next, with reference to FIGS. 5 and 6, a configuration of the exhaustgas purification device 27 will be described in detail. As illustratedin FIGS. 5 and 6, the exhaust gas purification device 27 includes thefirst case 28 having a double-tube structure constituted by a firstinner case 37 and a first outer case 38, the second case 29 having adouble-tube structure constituted by a second inner case 40 and a secondouter case 41, and the exhaust communicating tube 36 via which the firstcase 28 and the second case 29 are connected to each other. Theoxidation catalyst 30 is disposed inside the first inner case 37 that ismade of a heat-resistant metallic material and has a substantiallycylindrical shape, and the first inner case 37 is disposed inside thefirst outer case 38 that is made of a heat-resistant metallic materialand has a substantially cylindrical shape. The SCR filter 31, the SCRcatalyst 32, and the ammonia slip catalyst 33 are disposed inside thesecond inner case 40 that is made of a heat-resistant metallic materialand has a substantially cylindrical shape, and the second inner case 40is disposed inside the second outer case 41 that is made of aheat-resistant metallic material and has a substantially cylindricalshape.

As illustrated in FIG. 5, the first case 28 is configured such that thefirst inner case 37 externally covers, via a heat insulating material 49that is in the shape of a mat and is made of ceramic fiber, theoxidation catalyst 30 that is a first exhaust gas purification body.Namely, the heat insulating material 49 is pressed into between theoxidation catalyst 30 and the first inner case 37 to protect theoxidation catalyst 30. In addition, the first outer case 38 externallycovers the first inner case 37 with, e.g., a ring-shaped spacer (notillustrated) fitted between the first outer case 38 and the first innercase 37 so that an outer peripheral surface of the first inner case 37and an inner peripheral surface of the first outer case 38 are apartfrom each other.

As illustrated in FIG. 6, the second case 29 is configured such that thesecond inner case 40 externally covers, via heat insulating materials 50to 52 each of which is in the shape of a mat and is made of ceramicfiber, the SCR filter 31, the SCR catalyst 32, and the ammonia slipcatalyst 33 that are a second exhaust gas purification body. Namely, theheat insulating materials 50 to 52 are respectively pressed into betweenthe SCR filter 31 and the second inner case 40, between the SCR catalyst32 and the second inner case 40, and between the ammonia slip catalyst33 and the second inner case 40 to protect the SCR filter 31, the SCRcatalyst 32, and the ammonia slip catalyst 33. In addition, the secondouter case 41 externally covers the second inner case 40 with, e.g., aring-shaped spacer (not illustrated) fitted between the second outercase 41 and the second inner case 40 so that an outer peripheral surfaceof the second inner case 40 and an inner peripheral surface of thesecond outer case 41 are apart from each other.

As illustrated in FIGS. 5 and 6, the first case 28 is configured suchthat the exhaust-gas downstream part 28 a, which is downstream of theoxidation catalyst 30 in the exhaust gas traveling direction, has asmaller diameter than that of the exhaust-gas-purification-body mountedpart 28 b, in which the oxidation catalyst 30 is mounted. Namely, partsof the first inner case 37 and the first outer case 38 corresponding tothe exhaust-gas downstream part 28 a respectively have smaller diametersthan those of parts of the first inner case 37 and the first outer case38 corresponding to the exhaust-gas-purification-body mounted part 28 b.The parts of the first inner case 37 and the first outer case 38corresponding to the exhaust-gas downstream part 28 a have through-holes53 to 56 arranged in the top-and-bottom direction.

Through the through-holes 53 and 54 respectively provided in upperportions of the first inner case 37 and the first outer case 38, aninjection-body mounting case 57 to which the urea-water injection body76 is fixed is inserted. The injection-body mounting case 57 is fixed inupper portions of the parts of the first inner case 37 and the firstouter case 38 corresponding to the exhaust-gas downstream part 28 a suchthat an outer peripheral surface of the injection-body mounting case 57is in contact with inner peripheries of the through-holes 53 and 54 ofthe first inner case 37 and the first outer case 38. With thisconfiguration, it is possible to guide urea water from the urea-waterinjection body 76 into the first inner case 37, and to prevent intrusionof urea water and/or an exhaust gas into a space between the first innercase 37 and the first outer case 38.

Through the through-hole 55 of the first inner case 37, the urea mixingtube 39 is inserted. Through the through-hole 56 of the first outer case38, the urea mixing tube 39 and an exhaust communicating tube 36, whichcovers an outer surface of the urea mixing tube 39, are inserted. Theexhaust communicating tube 36 is fixed in lower portions of the parts ofthe first inner case 37 and the first outer case 38 corresponding to theexhaust-gas downstream part 28 a. Specifically, an upstream end of theexhaust communicating tube 36 in the exhaust gas traveling direction isin contact with a portion of the outer peripheral surface of the firstinner case 37, the portion being outward from the through-hole 55. Inaddition, an outer peripheral surface of the exhaust communicating tube36 is in contact with an inner periphery of the through-hole 56 of thefirst outer case 38. An outer peripheral surface of the urea mixing tube39 is in contact with and fixed to an inner periphery of thethrough-hole 55 of the first inner case 37. In addition, an upstream endof the urea mixing tube 39 in the exhaust gas traveling direction isinserted to reach the injection-body mounting case 57. Consequently, aconnected portion between the first case 28 and the second case 29 canachieve a double-tube structure having a high heat insulating property.Furthermore, it is possible to prevent intrusion of urea water and/or anexhaust gas into the space between the first inner case 37 and the firstouter case 38.

The first inner case 37 and the first outer case 38 have respectiveexhaust-outlet-side ends to which an exhaust-outlet-side inner lid 58shaped in a circular disc is fixedly attached. In addition, anexhaust-outlet-side outer lid 59 is fixed to face an outer surface ofthe exhaust-outlet-side inner lid 58. The oxidation catalyst 30 has anend surface on a downstream side in the exhaust gas traveling direction,and this end surface of the oxidation catalyst 30 is apart from theexhaust-outlet-side inner lid 58 by a certain distance. Consequently, anupstream-side urea mixing chamber 60 is created between the oxidationcatalyst 30 and the exhaust-outlet-side inner lid 58 inside the part ofthe first inner case 37 corresponding to the exhaust-gas downstream part28 a. The upstream-side urea mixing chamber 60 receives the urea mixingtube 39 externally inserted thereinto.

As illustrated in FIGS. 5 and 6, the second case 29 is configured suchthat the exhaust-gas upstream part 29 a, which is upstream of the SCRfilter 31 in the exhaust gas traveling direction, has a smaller diameterthan that of the exhaust-gas-purification-body mounted part 29 b, inwhich the SCR filter 31, the SCR catalyst 32, and the ammonia slipcatalyst 33 are mounted. Namely, parts of the second inner case 40 andthe second outer case 41 corresponding to the exhaust-gas upstream part29 a respectively have smaller diameters than those of parts of thesecond inner case 40 and the second outer case 41 corresponding to theexhaust-gas-purification-body mounted part 29 b. Through-holes 61 and 62are respectively provided in upper portions of the parts of the secondinner case 40 and the second outer case 41 corresponding to theexhaust-gas upstream part 29 a. An exhaust inlet tube 63 is disposed onthe outer peripheral surface of the second inner case 40. An exhaustoutlet side of the exhaust inlet tube 63 covers the through-hole 61, andan exhaust inlet side of the exhaust inlet tube 63 protrudes outwardfrom the through-hole 62 of the second outer case 41.

Into the through-hole 61 of the second inner case 40, the urea mixingtube 39 is inserted. Into the exhaust inlet tube 63, the urea mixingtube 39 and the exhaust communicating tube 36, which covers the outersurface of the urea mixing tube 39, are inserted. The exhaustcommunicating tube 36 is fixed in upper portions of the parts of thesecond inner case 40 and the second outer case 41 corresponding to theexhaust-gas upstream part 29 a. Specifically, a downstream end of theexhaust communicating tube 36 in the exhaust gas traveling direction isin contact with a portion of the outer peripheral surface of the secondinner case 40, the portion being outward from the through-hole 61. Inaddition, the outer peripheral surface of the exhaust communicating tube36 is in contact with an inner periphery of the exhaust inlet of theexhaust inlet tube 63. The outer peripheral surface of the urea mixingtube 39 is in contact with and fixed to an inner periphery of thethrough-hole 61 of the second inner case 40. In addition, a downstreamend of the urea mixing tube 39 in the exhaust gas traveling direction isinserted to reach the inside of the second inner case 40. Consequently,a connected portion between the first case 28 and the second case 29 canachieve a double-tube structure having a high heat insulating property.Furthermore, it is possible to prevent intrusion of urea water and/or anexhaust gas into a space between the second inner case 40 and the secondouter case 41.

The second inner case 40 and the second outer case 41 have respectiveexhaust-inlet-side ends to which an exhaust-inlet-side inner lid 64shaped in a circular disc is fixedly attached. In addition, anexhaust-inlet-side outer lid 65 is fixed to face an outer surface of theexhaust-inlet-side inner lid 64. The SCR filter 31 has an end surface onan upstream side in the exhaust gas traveling direction, and this endsurface of the SCR filter 31 is apart from the exhaust-inlet-side innerlid 64 by a certain distance. Consequently, a downstream-side ureamixing chamber 66 is created between the SCR filter 31 and theexhaust-inlet-side inner lid 64 inside the part of the second inner case40 corresponding to the exhaust-gas upstream part 29 a. Thedownstream-side urea mixing chamber 66 receives the urea mixing tube 39externally inserted thereinto.

As illustrated in FIGS. 5 and 6, the urea-water injection body 76 isattached, via an injection seat 77, to the injection-body mounting case57 disposed in the exhaust-gas downstream part 28 a of the first case28. The urea-water injection body 76 sprays an aqueous urea solutioninto the upstream-side urea mixing chamber 60 in the first inner case37. The urea-water injection body 76 has a urea-water injection valve 78protruding downward to be inserted into a nozzle mounting hole 79provided in the injection seat 77. The urea-water injection body 76 isdisposed on the injection-body mounting case 57 such that the positionof the nozzle mounting hole 79 penetrating through the injection seat 77coincides with the position of a urea-water guide hole 80 penetratingthrough the injection-body mounting case 57. Consequently, urea waterinjected from the urea-water injection valve 78 of the urea-waterinjection body 76 is guided, through the nozzle mounting hole 79 and theurea-water guide hole 80, into the urea mixing tube 39 disposed insidethe upstream-side urea mixing chamber 60.

As illustrated in FIGS. 5 and 6, the urea mixing tube 39 has a mixingtube inlet 81 at an upper end of the urea mixing tube 39, and also has amixing tube outlet 82 at a lower end of the urea mixing tube 39. Themixing tube inlet 81 is inserted into the upstream-side urea mixingchamber 60 created near the exhaust outlet of the first case 28, whereasthe mixing tube outlet 82 is inserted into the downstream-side ureamixing chamber 66 created near the exhaust inlet of the second case 29.The urea mixing tube 39 has an intermediate portion between the firstcase 28 and the second case 29, and an outer peripheral surface of theintermediate portion is covered with the exhaust communicating tube 36,which is connected to the first case 28 and the second case 29. Thus,the urea mixing tube 39 is covered with the first case 28, the secondcase 29, and the exhaust communicating tube 36. This provides a heatinsulating layer over the outer peripheral surface of the urea mixingtube 39. Consequently, the inside of the urea mixing tube 39 can bemaintained at a high temperature. This makes it possible to suppress orreduce the phenomenon that a crystal lump of a urea component is formedin the urea mixing tube 39.

The urea mixing tube 39 has the end serving as the mixing tube inlet 81with a obliquely-cut shape (a obliquely-cut circular cylinder shape).Specifically, the mixing tube inlet 81 of the urea mixing tube 39 has atube wall becoming lower from a side close to the oxidation catalyst 30(i.e., the oxidation catalyst 30 side) toward a side close to theexhaust-outlet-side inner lid 58. Namely, the mixing tube inlet 81 ofthe urea mixing tube 39 is configured such that a portion of the tubewall on the oxidation catalyst 30 side is in contact with a portion ofan inner peripheral surface of the injection-body mounting case 57, theportion being outward from the urea-water guide hole 80. Consequently,the mixing tube inlet 81 of the urea mixing tube 39 is configured tohave a closed space on the oxidation catalyst 30 side. Meanwhile, themixing tube inlet 81 of the urea mixing tube 39 is opened toward theexhaust-outlet-side inner lid 58. An inner peripheral surface of themixing tube inlet 81 of the urea mixing tube 39 is located outward fromthe urea-water guide hole 80 of the injection-body mounting case 57. Thetube wall of the urea mixing tube 39 has an inserted portion that isinserted into the first case 28. This inserted portion has a pluralityof exhaust introduction holes 83 and thus is porous.

As described above, the tube wall of the mixing tube inlet 81 of theurea mixing tube 39 has a height increasing toward the oxidationcatalyst 30. Due to such a shape of the mixing tube inlet 81, most of anexhaust gas having passed through the oxidation catalyst 30 makes adetour and is introduced into the urea mixing tube 81 from theexhaust-outlet-side inner lid 58 side. Thus, the obliquely-cut openingand the exhaust introduction holes 83 of the mixing tube inlet 81 eachfunction as an exhaust introduction opening allowing an exhaust gas tobe introduced into the urea mixing tube 39. Consequently, a flowvelocity of the exhaust gas introduced into the urea mixing tube 39 canbe made uniform. As a result, urea water sprayed from the urea-waterinjection valve 78 toward the mixing tube inlet 81 of the urea mixingtube 39 becomes more likely to be stirred and dispersed. This improvesthe evaporativity of the urea component at a low temperature, and alsoenhances the reaction efficiency between the exhaust gas and the ureacomponent.

The urea mixing tube 39 has the end serving as the mixing tube outlet 82and being narrowed (tapered) toward a distal end thereof. Namely, adiameter of the mixing tube outlet 82 is reduced toward the distal end.In addition, the mixing tube outlet 82 extends toward a portion of aninner wall surface of the second case 29, the portion being opposite tothe exhaust inlet tube 63. Although the mixing tube outlet 82 of theurea mixing tube 39 extends into the second inner case 40 of the secondcase 29, the mixing tube outlet 82 is located apart from an inner wallsurface of the second inner case 40.

As described above, the mixing tube outlet 82 of the urea mixing tube 39is squeezed toward the distal end. Due to such a shape of the mixingtube outlet 82, urea water is caused to collide with an inner wallsurface of the mixing tube outlet 82 at the distal end. Thus, theexhaust gas and an unreacted urea component are caused to collide withthe mixing tube outlet 82, so as to be evaporated. This facilitates areaction between the exhaust gas and the urea component in thedownstream-side urea mixing chamber 66 in the second case 29.Furthermore, it is possible to prevent the urea component from reachingthe inner wall surface of the second inner case 40, thereby suppressingor reducing the phenomenon that a crystal lump is formed on the innerwall surface of the second inner case 40.

The urea mixing tube 39 internally includes, at a location downstream ofthe portion in which the exhaust introduction holes 83 are bored, amixer 84 for facilitating mixing of the urea water and the exhaust gastogether. For example, the mixer 84 includes a plurality of bladesarranged radially in point symmetry with respect to a central axis ofthe urea mixing tube 39. The mixer 84 causes the urea water to be mixedand dispersed in the exhaust gas. The mixer 84 is disposed at a locationfrom which the urea mixing tube 39 is inserted into the second case 29(i.e., a location near the through-holes 61 and 62). Thus, the mixer 84is fixed at a location upstream of the mixing tube outlet 82 of the ureamixing tube 39 when viewed in the exhaust gas traveling direction.

As described above, the mixer 84 is disposed inside the second case 29,which has a high heat-insulating property. Consequently, it is possibleto suppress or reduce a temperature drop in the mixer 84. In addition,since the exhaust gas whose flow velocity has been made uniform at themixing tube inlet 81 flows into the mixer 84, the mixer 84 achievesrotatability free from fluctuations. This facilitates mixing of the ureawater with the exhaust gas, thereby making it possible to enhance theevaporativity of the urea component. Thus, the above configuration canprevent crystallization of the urea component in the mixer 84. Not onlythis, the above configuration can facilitate a reaction between theexhaust gas and the urea component, and can suppress or reduce thephenomenon that the urea water in the form of droplets enters the secondcase 29. In addition, due to the configuration in which the mixing tubeoutlet 82 downstream of the mixer 84 has a tapered shape, the urea waterhaving passed through the mixer 84 and being in the form of droplets iscaused to collide with the mixing tube outlet 82. This prevents the ureacomponent from reaching the inner wall surface of the second inner case40.

<First Modification of Urea Mixing Tube>

Next, with reference to FIGS. 7 and 8, a first modification of the ureamixing tube 39 will be described. In the present modification, asillustrated in FIGS. 7 and 8, a mixing tube inlet 81 of a urea mixingtube 39 has a bell-mouth shape. In addition, the mixing tube inlet 81has an expanded distal end and is in contact with a portion of aninjection-body mounting case 57, the portion being outward from aurea-water guide hole 80 of the injection-body mounting case 57. Theurea mixing tube 39 has an inserted portion that is inserted into afirst case 28. A tube wall of the inserted portion of the urea mixingtube 39 is partially bent toward the inside of the urea mixing tube 39,and the bent part of the tube wall functions as a urea collision plate85. As a result of cutting the tube wall of the urea mixing tube 39 toyield the urea collision plate 85, an opening is created. This openingfunctions as an exhaust introduction opening 86 allowing an exhaust gashaving passed through an oxidation catalyst 30 to be introduced into theurea mixing tube 39.

The urea mixing tube 39 includes a plurality of urea collision plates 85that are bent parts of the tube wall of the urea mixing tube 39. Each ofthe urea collision plates 85 extends in a direction toward the center ofthe urea mixing tube 39 and away from a urea-water injection valve 78.The urea mixing tube 39 has the exhaust introduction openings 86 eachopened downward from a position at which a respective one of the ureacollision plates 85 is bent. Consequently, the urea mixing tube 39 has areduced diameter, i.e., is narrowed (squeezed) at a location in whichthe urea collision plates 85 are provided. The urea mixing tube 39 has ashape whose cross-section is continuously increased toward a downstreamside (downward) from the location at which the urea collision plates 85are provided.

Due to the configuration in which the mixing tube inlet 81 of the ureamixing tube 39 has a bell-mouth shape, a urea component from theurea-water injection valve 78 is hardly adhered to the tube wall of theurea mixing tube 39. Furthermore, due to the configuration in which theinserted portion of the urea mixing tube 39 that is inserted into thefirst case 28 is squeezed at the location in which the exhaustintroduction openings 86 are provided, it is possible to increase a flowvelocity of an exhaust gas introduced through the exhaust introductionopenings 86, thereby facilitating a temperature increase in the tubewall of the urea mixing tube 39. Moreover, due to the configuration inwhich the tube wall of the urea mixing tube 39 is gradually expandedtoward lower through-holes 55 and 56 of the first case 28, it ispossible to suppress or reduce a temperature drop in the tube wall ofthe urea mixing tube 39. Consequently, it is possible to reduce thephenomenon that a crystal lump of a urea component is formed, on aninner wall surface of the urea mixing tube 39, thereby making itpossible to easily prevent an increase in exhaust resistance in the ureamixing tube 39 that may otherwise be caused by, e.g., growth of the ureacrystal lump.

Due to the configuration in which the urea mixing tube 39 includes theurea collision plates 85 located downstream (downward) of the urea-waterinjection valve 78, urea water injected from the urea-water injectionvalve 78 is caused to collide with the urea collision plates 85.Consequently, the urea water can be easily made into fine particles.This facilitates a reaction between the urea component and the exhaustgas. With a greater inclination angle (an angle at which the urea watercollides with each of the urea collision plates 85) of each of the ureacollision plates 85 with respect to a direction in which the urea wateris injected from the urea-water injection valve 78, the urea waterhardly forms a liquid membrane on the parts of the tube wallcorresponding to the urea collision plates 85. Consequently, it ispossible to suppress or reduce formation of a crystal lump of the ureacomponent.

In addition, due to the configuration in which the urea collision plates85 are made of the parts of the tube wall of the urea mixing tube 39 andthe exhaust introduction openings 86 are provided in the tube wall ofthe urea mixing tube 39, the urea collision plates 85 are exposed to theexhaust gas having a high temperature and accordingly the temperaturesof the urea collision plates 85 can be increased. Consequently, even ina case where the urea water injected from the urea-water injection valve78 collides with the urea collision plates 85, it is possible tosuppress or reduce the phenomenon that a crystal lump of the ureacomponent is formed on the urea collision plates 85.

In addition, the inserted portion of the urea mixing tube 39 that isinserted into the first case 28 is squeezed at a location downstream ofthe mixing tube inlet 81, and the urea collision plates 85 are providedat the squeezed location. This configuration makes it possible toincrease a flow velocity of the exhaust gas at the location in which theurea collision plates 85 are provided. This facilitates heat exchangebetween the urea collision plates 85 and the exhaust gas. Consequently,it is possible to effectively increase the temperatures of the ureacollision plates 85.

<Second Modification of Urea Mixing Tube>

Next, with reference to FIGS. 9 and 10, a second modification of theurea mixing tube 39 will be described. In the present modification, asillustrated in FIGS. 9 and 10, a mixing tube outlet 82 of a urea mixingtube 39 has an outer peripheral surface provided with a plurality ofheat exchange fins 87 protruding outwardly. Due to the heat exchangefins 87 provided to the mixing tube outlet 82, it is possible tosuppress or reduce, by a temperature atmosphere in a second case 29, atemperature drop in a tube wall of an inserted portion of the mixingtube outlet 82, the inserted portion having been inserted into adownstream-side urea mixing chamber 66. Consequently, it is possible toimprove the evaporativity of a urea component that collides with thetube wall of the mixing tube outlet 82, thereby facilitating a reactionbetween the urea component and an exhaust gas. Note that the presentmodification can be combined with the configuration of the firstmodification.

Second Embodiment

With reference to the drawings (FIGS. 11 to 14), the following willdescribe a second embodiment in which the present invention isimplemented. FIG. 11 is a right side view of a diesel engine 1, showinga right side on which an exhaust manifold 6 is disposed. FIG. 12 is aplan view of the diesel engine 1, showing a side on which a cylinderhead cover 12 is disposed. FIG. 13 is a back view of the diesel engine1, showing a side on which a flywheel housing 8 is disposed. Note thatcomponents and parts/portions of an engine device of the presentembodiment identical to those of the engine device of the firstembodiment are given identical reference signs, and detailed descriptionthereof is omitted.

With reference to FIGS. 11 to 14, the following will describe aconnection structure of an exhaust gas purification device 27 accordingto the present embodiment. As illustrated in FIGS. 11 to 14, in theexhaust gas purification device 27 of the present embodiment, aurea-water injection body 76 is fixed to a portion of an outerperipheral surface of an exhaust-gas downstream part 28 a of a firstcase 28, the portion being located inward (i.e., closer to the cylinderhead cover 12) from the top of the first case 28.

Parts of a first inner case 37 and a first outer case 38 of the firstcase 28 corresponding to the exhaust-gas downstream part 28 arespectively have through-holes 53 and 54 located leftward of the top ofthe first case 28 (i.e., closer to the cylinder head cover 12). Aninjection-body mounting case 57 is mounted through the through-holes 53and 54 in the first case 28 such that the injection-body mounting case57 extends obliquely toward the lower right. Consequently, a surface ofthe injection-body mounting case 57 on which the urea-water injectionbody 76 is to be mounted is inclined toward the cylinder head cover 12(to the left). Thus, the urea-water injection body 76 is mountedinclined. As a result, the urea-water injection body 76 is supported ata low position above the diesel engine 1. Thus, the top surface side ofthe diesel engine 1 can be made low.

The urea mixing tube 39 is inserted into the first case 28 from a lowerportion of the first case 28, the lower portion being outside of andlateral to (at the right side of) the engine device. In addition, amixing tube inlet 81 of the urea mixing tube 39 extends toward theurea-water injection body 76 (toward the upper left). Namely, the mixingtube inlet 81 of the urea mixing tube 39 is inserted into the firstinner case 37 through through-holes 55 and 56 located in the lowerportion of the first case 28, the lower portion being outside of andlateral to (at the right side of) the engine device. The urea mixingtube 39 has an intermediate portion that is bent in a second case 29 sothat a mixing tube outlet 82 is inserted into the second case 29orthogonally to a longitudinal direction of the second case 29.

An exhaust communicating tube 36 is obliquely disposed such that theexhaust communicating tube 36 is inclined toward the cylinder head 2(toward the left) relative to a direction orthogonal (vertical) to thelongitudinal direction of the second case 29. Via the exhaustcommunicating tube 36, an exhaust inlet tube 63 protruded from a secondouter case 41 and the through-hole 56 of the first outer case 38communicate with each other. In addition, the exhaust communicating tube36 covers an outer peripheral surface of the intermediate portion of theurea mixing tube 39. The bent portion of the urea mixing tube 39 islocated in the vicinity of through-holes 61 and 62 of the second case29, and is covered with the exhaust communicating tube 36 and theexhaust inlet tube 63. Due to the configuration in which the bentportion of the urea mixing tube 39 is located inside the second case 29,a temperature of the tube wall of the bent portion can be increased to ahigh temperature. Consequently, it is possible to suppress or reducecrystallization of a urea component that collides with an inner wallsurface of the exhaust communicating tube 36.

A mixer 84 is disposed in an inserted portion of the urea mixing tube 39that is inserted into the first case 28. The mixer 84, which facilitatesmixing of urea water and an exhaust gas together, is internally includedin the urea mixing tube 39, and is located downstream of a portion ofthe urea mixing tube 39 in which exhaust introduction holes 83 arebored. In the present embodiment, the mixer 84 is located in thevicinity of the lower through-holes 55 and 56 of the first case 28. Byplacing the mixer 84 inside the first case 28, the mixer 84 can be underan environment of a high-temperature exhaust gas. Consequently, it ispossible to improve evaporation performance achieved with the mixer 84.Not only this, it is possible to suppress or reduce formation of acrystal lump of a urea component, thereby facilitating a reactionbetween the urea component and an exhaust gas.

In the present embodiment, the mixer 84 is disposed inside the firstcase 28, and thus a distance between the mixer 84 and the mixing tubeoutlet 82 in the urea mixing tube 39 is long. Thanks to this, the mixingtube outlet 82 can emit the exhaust gas in which the urea component isadequately stirred and mixed. In the above configuration, the mixingtube outlet 82 of the urea mixing tube 39 inserted into the second case29 is squeezed to be tapered, in a similar manner to the firstembodiment. However, in view of the above effect, the urea mixing tube82 may have a shape whose tube diameter is constant to its distal end.In the present embodiment, a portion of the urea mixing tube 39 close tothe mixing tube inlet 81 may have a similar shape to that of the firstmodification of the first embodiment. Also, a portion of the urea mixingtube 39 close to the mixing tube outlet 82 may be provided with a heatexchange fin 87 in a similar manner to the second modification of thefirst embodiment.

<Examples of Applications of First and Second Embodiments>

With reference to FIGS. 15 and 16, the following will describe aconfiguration of an excavator 100 in which the diesel engine 1 accordingto the first or second embodiment is mounted. As illustrated in FIGS. 15and 16, the excavator 100 includes a crawler-type traveling device 102having a pair of left and right traveling crawlers 103 and a slewingbody 104 provided above the traveling device 102. The slewing body 104is horizontally turnable in all directions of 360° by a hydraulic motor(not illustrated) for slewing. The slewing body 104 has a front leftportion in which a cabin (operation unit) 106 is mounted. The slewingbody. 104 has a front center portion in which a work unit 110 providedwith a boom 111 and a bucket 113 each used for an excavation work ismounted. The slewing body 104 has a rear portion in which a radiator 19and the diesel engine 1 are mounted. The slewing body 104 has a rightside portion in which a fuel tank 45 and a urea water tank 71 aremounted.

In the cabin 106, an operator's seat on which an operator sits and alever or a switch used as an operation means for operating an output of,e.g., the diesel engine 1 and/or an operation means for the work unit110 are disposed. The boom 111, which is a component of the work unit110, is provided with a boom cylinder 112 and a bucket cylinder 114. Theboom 111 has a distal end at which a bucket 113 that is an attachmentfor excavation is pivotably attached such that the bucket 113 isturnable for scooping. By actuating the boom cylinder 112 or the bucketcylinder 114, the bucket 113 is actuated to perform an earthwork (aground work such as furrowing).

The slewing body 104 has a rear left portion in which the radiator 19 ismounted. On the right side of the radiator 19, the diesel engine 1 ismounted such that a cooling fan 24 of the diesel engine 1 faces theradiator 19. The diesel engine 1 is disposed such that the side on whichthe exhaust manifold 6 is mounted faces the cabin 106 and the work unit110. In addition, the top surface of the diesel engine 1 is covered witha hood 115. The first case 28 of the exhaust gas purification device 27is disposed behind the work unit 110, and the second case 29 of theexhaust gas purification device 27 extends rearward from the connectedportion between the first case 28 and the second case 29. The tail pipe116, which is connected to the exhaust outlet of the second case 29,protrudes upward from a rear portion of the hood 115.

The fuel tank 45 and the urea water tank 71, which are disposed in theright side portion of the slewing body 104, are arranged side by side ina front-and-rear direction. The fuel tank 45 and the urea water tank 71are respectively provided with a fuel inlet 46 and a water inlet 72 eachprotruding toward the right. In addition, a urea water injection pump 73for forcibly feeding an aqueous urea solution in the urea water tank 71is interposed between the urea water tank 71 and the first case 28.Consequently, urea water pipe arrangement for connecting the urea-waterinjection body 76 fixed to the first case 28 and the urea water pump 73to each other can be made shorter. Furthermore, urea water pipearrangement for connecting the urea water tank 71 and the urea waterpump 73 to each other can also be made shorter.

Third Embodiment

With reference to the drawings (FIGS. 17 to 19), the following willdescribe a third embodiment in which the present invention isimplemented. Note that components and parts/portions of an engine deviceof the present embodiment identical to those of the engine device of thesecond embodiment are given identical reference signs, and detaileddescription thereof is omitted.

As illustrated in FIG. 17, a diesel engine 1 of the present embodimentincludes an exhaust gas purification device 27 including a first case 28disposed on a top surface of the diesel engine 1 and a second case 29disposed remotely from the diesel engine 1. An exhaust outlet of thefirst case 28 and an exhaust inlet of the second case 29 communicatewith each other via an exhaust connecting tube 177 having an L-shape. Inaddition, the exhaust connecting tube 177 internally includes a ureamixing tube 176. Consequently, a connected portion between the firstcase 28 and the second case 29 has a double-tube structure.

Similarly to the second embodiment, the urea mixing tube 176 has amixing tube inlet 81 inserted into an exhaust-gas downstream part 28 aof the first case 28. Similarly to the second embodiment, the mixingtube inlet 81 of the urea mixing tube 176 is configured to have an endthat is obliquely cut, to have exhaust introduction holes 83, and tointernally include a mixer 84 (see FIG. 6).

In addition, similarly to the second embodiment, the urea mixing tube176 has a mixing tube outlet 82 inserted into an exhaust-gas upstreampart 29 a of the second case 29. Similarly to the second embodiment, themixing tube inlet 81 of the urea mixing tube 176 has a distal end thatis squeezed. Note that, similarly to the first and second embodiments,the configurations of the urea mixing tubes 176 according to the firstand second modifications may be applied to the urea mixing tube 176 ofthe present embodiment.

<Examples of Applications of Third Embodiment>

With reference to FIGS. 17 to 19, the following will describe a tractor151 in which the diesel engine 1 of the third embodiment is mounted. Asillustrated in FIGS. 17 to 19, a tractor 151 for an agricultural workthat is a work vehicle includes: a carriage 152 supported by a pair ofleft and right front wheels 153 and a pair of left and right rear wheels154; and the diesel engine 1 mounted in a front portion of the carriage152. The diesel engine 1 is driven to drive the rear wheels 154 and thefront wheels 153 to cause the tractor 151 to run forward or backward.The top surface and the left and right side surfaces of the dieselengine 1 are covered with a hood 156 that is openable.

In addition, a cabin (operation unit) 157 on which an operator is toride is mounted on a portion of a top surface of the carriage 152, theportion being behind the hood 156. The cabin 157 includes, in itsinside, an operator's seat 158 on which the operator is to sit and asteering instrument such as a steering wheel 159 that is a steeringmeans. In addition, a pair of left and right steps 160, which can beused when the operator gets in or off the cabin 157, are providedoutside of left and right sides of the cabin 157, respectively. In aspace inward from the steps 160 and below a bottom of the cabin 157, afuel tank 45 from which a fuel is supplied to the diesel engine 1 isdisposed.

The carriage 152 includes a transmission case 161 for changing an outputfrom the diesel engine 1 and transmitting the output to the rear wheels154 (the front wheels 153). The transmission case 161 has a rear portionto which a machine such as a tilling machine (not illustrated) isconnected, e.g., via a lower link 162, a top link 163, and a lift arm164 in such a manner that the tilling machine can be raised and lowered.In addition, a power take-off (PTO) shaft 165 for driving, e.g., thetilling machine is disposed in a rear side surface of the transmissioncase 161. The carriage 152 of the tractor 151 includes, e.g., the dieselengine 1, the transmission case 161, and a clutch case 166 by which thediesel engine 1 and the transmission case 161 are connected to eachother.

In addition, the second case 29 is attached to a right corner portion ina front surface of the cabin 157 so that the second case 29 is uprightand vertically long. A tail pipe 178 is disposed upright to extend fromthe exhaust outlet side of the second case 29. Namely, at the rightcorner portion in the front surface of the cabin 157, the tail pipe 178and the second case 29 are arranged in series in the top-and-bottomdirection. The exhaust inlet tube 63 of the second case 29 is connectedto the exhaust outlet of the first case 28 under the hood 156 via theexhaust connecting tube 177 having, in its intermediate portion, abellows-tube type flexible tube 179.

The urea water tank 71 is disposed at a portion of the front surface ofthe cabin 157, the portion corresponding to a left side of the hood 156and being opposite to the right side on which the tail pipe 178 isdisposed. Namely, the urea water tank 71 is mounted on a portion of thecarriage 152 (e.g., on a portion of a bottom frame of the cabin 157),the portion corresponding to a rear left portion of the hood 156. To alower left portion of the front surface of the cabin 157, the fuel inlet46 of the fuel tank 45 and the water inlet 72 of the urea water tank 71are disposed adjacent to each other. The tail pipe 178 is disposed in aportion of the front surface of the cabin 157 on the right side, throughwhich the operator seldom gets in and off the cabin 157. Meanwhile, thefuel inlet 46 and the water inlet 72 are disposed in a portion of thefront surface of the cabin 157 on the left side, through which theoperator often gets in and off the cabin 157. Note that the cabin 157 isconfigured such that the operator can get to and leave the operator'sseat 158 through either of the left side and the right side of the cabin157.

In addition, the urea water injection pump 73 for forcibly feeding anaqueous urea solution in the urea water tank 71 is interposed betweenthe urea water tank 71 and the first case 28. Consequently, urea waterpipe arrangement for connecting the urea-water injection body 76 fixedto the first case 28 and the urea water injection pump 73 to each othercan be made shorter. Furthermore, urea water pipe arrangement forconnecting the urea water tank 71 and the urea water injection pump 73to each other can also be made shorter. Thus, efficient urea water pipearrangement can be achieved. Consequently, it is possible to simplify apiping work and a maintenance work. Not only this, it is possible toreduce influences given by an external environment on the urea waterpipe arrangement, thereby suppressing or reducing crystallization ofurea water in the urea water pipe arrangement.

Note that the configurations of the parts/portions of the presentinvention are not limited to those in the illustrated embodiments, andcan be modified and changed in various ways unless such modificationsand changes depart from the scope of the present invention. For example,the configurations of the embodiments described above may be applied toan exhaust gas processing device including: a first case that is a DPFcase including an oxidation catalyst and a soot filter as a firstexhaust gas purification body; and a second case that is an SCR caseincluding an SCR catalyst and an ammonia slip catalyst as a secondexhaust gas purification body. In the embodiments described above, themixer includes the blades that are fixed. Alternatively, a mixerincluding rotatable blades may be employed.

REFERENCE SIGNS LIST

-   -   1 diesel engine    -   27 exhaust gas purification device    -   28 first case    -   29 second case    -   30 oxidation catalyst    -   31 SCR filter    -   32 SCR catalyst    -   33 ammonia slip catalyst    -   36 exhaust communicating tube    -   37 first inner case    -   38 first outer case    -   39 urea mixing tube    -   40 second inner case    -   41 second outer case    -   76 urea-water injection body    -   78 urea-water injection valve    -   79 nozzle mounting hole    -   80 urea-water guide hole    -   81 mixing tube inlet    -   82 mixing tube outlet    -   83 exhaust introduction hole    -   84 mixer    -   85 urea collision plate    -   86 exhaust introduction opening    -   87 heat exchange fin

1. An engine device comprising: an exhaust gas purification deviceincluding a first case communicating with an exhaust manifold of anengine and internally including a first exhaust gas purification bodyfor removing a carbon compound and a second case communicating with anexhaust outlet of the first case and internally including a secondexhaust gas purification body for removing a nitrogen compound, whereinthe first and second cases are arranged above the engine and in anL-shape to respectively extend along two side surfaces of the engine,the two side surfaces being adjacent to each other and comprising afirst side and a second side, and the second case is disposed below thefirst case, and the first case and the second case are connected to eachother via a urea mixing tube in a position in which the first case andthe second case overlap each other in a plan view.
 2. The engine deviceaccording to claim 1, wherein a turbocharger is interposed between thefirst case and the exhaust manifold, and the first case and theturbocharger are connected to each other in series above the exhaustmanifold disposed close to the first side surface.
 3. The engine deviceaccording to claim 2, wherein a flywheel housing is disposed close tothe second side surface intersecting the first side surface, and thesecond case is disposed above the flywheel housing.
 4. (canceled)
 5. Theengine device according to claim 1, wherein a urea-water injection bodyfor injecting urea water into the first case is fixed to a portion of anouter peripheral surface of the first case, the portion being in aposition in which the first case and the second case overlap each otherin a plan view, and the portion being not a portion of the first casethrough which the urea mixing tube is inserted into the first case. 6.The engine device according to claim 1, wherein a part of the secondexhaust gas purification body is a selective catalytic reduction filtermade of a particulate-matter collection filter to which a catalyticcomponent for urea selective catalytic reduction is applied.
 7. Anengine device comprising: an exhaust gas purification device including afirst case communicating with an exhaust manifold of an engine andinternally including a first exhaust gas purification body for removinga carbon compound and a second case communicating with an exhaust outletof the first case and internally including a second exhaust gaspurification body for removing a nitrogen compound, wherein the firstand second cases are arranged above the engine and in an L-shape torespectively extend along two side surfaces of the engine, the two sidesurfaces being adjacent to each other, a urea-water injection body forinjecting urea water into a urea mixing tube is disposed in a portion ofthe first case that is close to the exhaust outlet of the first case,and the urea mixing tube has both ends respectively inserted into theexhaust outlet of the first case and an exhaust inlet of the second caseto allow the first case and the second case to communicate with eachother, and the second case is disposed below the first case, and thefirst case and the second case are connected to each other via the ureamixing tube in a position in which the first case and the second caseoverlap each other in a plan view.
 8. The engine device according toclaim 7, wherein the urea mixing tube has a first inserted portion thatis inserted into the first case, the first inserted portion extendingtoward the urea-water injection body, the first inserted portion havinga tube wall on which an exhaust introduction opening is bored, and theexhaust introduction opening allowing an exhaust gas having passedthrough the first exhaust gas purification body to be introduced intothe urea mixing tube.
 9. The engine device according to claim 7, whereinthe urea mixing tube has a second inserted portion that is inserted intothe second case, the second inserted portion having a distal end that istapered, and the second inserted portion extending to a position apartfrom an inner wall surface of the second case.
 10. The engine deviceaccording to claim 8, wherein a mixer for stirring and mixing urea waterwith an exhaust gas is internally included in a second inserted portionof the urea mixing tube, the second inserted portion being inserted intothe second case.
 11. The engine device according to claim 8, wherein amixer for stirring and mixing urea water with an exhaust gas is disposedin the first inserted portion of the urea mixing tube, the firstinserted portion being inserted into the first case.
 12. (canceled)